This invention relates generally to a container for a fluid breath alcohol simulator solution used to calibrate breath alcohol testing equipment, and a method for using such a container with breath alcohol simulators.
Several methods exist for directly or indirectly testing blood alcohol concentrations in individuals. Among the indirect methods, the most frequently used is breath alcohol testing Breath alcohol testing involves measuring the alcohol vapor level or concentration in a contained sample of expelled breath, that concentration being proportionally related to the individual's blood alcohol level.
Breath alcohol testers (commonly referred to as Breathalyzers.TM.) generally function using one of two conventional methods: fuel cells or infra-red absorption.
Breath is expelled under pressure through a tube having a gas pressure sensor into a chamber having a predetermined volume. The temperature of the gas may also be measured, or a standard body temperature constant may be utilized. The pressure sensor is coupled to a control circuit which calculates when the volume of air having entered the chamber reaches the predetermined volume, and either closes a control valve in response to a predetermined volume of air being admitted or signals the operator to cease expelling air.
In a fuel cell type breath alcohol tester, the predetermined volume of air contained within the chamber is passed between two platinum electrodes The alcohol vapor in the air produces a chemical reaction with the platinum electrodes, the extent or rate of the reaction being proportional to the concentration of alcohol molecules in the air contacting the platinum electrodes. The chemical reaction stimulates an electric voltage in or between the electrodes which is proportional to the concentration of alcohol molecules incident with the electrodes. A microprocessor measures the voltage and translates that value to either a breath alcohol concentration or an estimated blood alcohol concentration.
In an infra-red absorption type breath alcohol tester, one or more infra-red light beams are directed through the predetermined volume of air. A spectrometer or infra-red sensors measure the percentage of infra-red radiation at a discrete frequency which is transmitted through the air. The frequency of the infra-red radiation measured corresponds to the frequency which is absorbed by ethanol molecules The percentage of absorbed infra-red radiation (or the reciprocal of the transmitted radiation) is proportional to the concentration of alcohol molecules within the air, and a microprocessor determines the value of the absorbed infra-red radiation and translates that value to either a breath alcohol concentration or an estimated blood alcohol concentration The chamber of the breath alcohol tester is then purged, and a new sample may be collected.
In practice, both fuel cell or infra-red absorption breath alcohol testers must be calibrated periodically. Statutes and regulations proscribing the use of breath alcohol testers in criminal investigations or substance abuse testing vary between jurisdictions, however recalibration as frequently as every twenty tests is a common rule, and recalibration as a part of each test may be called for in some circumstances.
In order to calibrate the breath alcohol testers, it is necessary to introduce a gas having a known alcohol vapor concentration into the chamber of the breath alcohol tester under normal operating conditions. This is accomplished using a device known as a breath alcohol simulator.
In principle, the breath alcohol simulator functions by passing or bubbling air (or an inert gas) through a simulator solution or liquid having a fixed fluid concentration of alcohol and a controlled temperature. The air or gas absorbs a specific molar amount of alcohol molecules, and is therefore expelled from the breath alcohol simulator having a known alcohol-to-air concentration. For example, a simulator solution may be prepared so that when it is utilized in a particular type of breath alcohol simulator, the air expelled by the breath alcohol simulator will have an alcohol concentration equivalent to a specific reading (breath alcohol or estimated blood alcohol) to be displayed by the breath tester, most frequently a critical value for legal intoxication.
Through laboratory analysis and certification of samples of the simulator solution, operators of breath testers and breath simulators can be assured that the equipment is providing uniform and accurate measurements when used.
Representative examples of various types of this and other types of breath alcohol simulators are shown in U.S. Pat. Nos. 4,407,152 to Guth; 3,948,604 to Hoppesch; 3,854,319 to Burroughs; 4,495,418 to Hutson; 4,391,777 to Hutson; 3,847,551 to Hutson; 3,842,345 to Padgitt; and D291,355 to Stanuch.
The simulator solutions provided for use in the breath alcohol simulators are currently packaged and provided in containers such as 500 cc white polyethylene bottles. These bottles are thick walled, and pursuant to increasing environmental regulations must be cleaned and recycled rather than disposed. This necessitates that a large supply of bottles be carried in some type of a case or carton, with the empty bottles being replaced in the carton and returned to a central dispatch or supplier. This can be very inconvenient for police or other law enforcement officers who can carry only a limited amount of equipment or supplies, and those involved with testing large numbers of people as part of an federal, state, or private employee substance abuse testing programs In cold climates, water-based simulator solution can freeze despite the ethanol content, and the expansion upon freezing can crack or destroy the bottles In many instances this will only produce an inconvenient clean- up problem and possibly damage other equipment, but if undetected can cause a degradation or contamination of the simulator solution that will adversely affect the validity of the calibration.
Moreover, one potential source of error may be found in the manner in which the simulator solution is used. Since the simulator solution which is placed in the bottles must be analyzed and certified for accuracy, the bottles must also be sealed with a tamper-resistant or tamper-evidencing closure, or it is possible that the simulator solution may be contaminated or corrupted prior to use in calibrating the breath testing equipment. Once opened, the simulator solution may be spilled (affecting the total volume of fluid placed in the simulator) or allowed to evaporate (affecting the alcohol concentration of the simulator solution.) There is also the possibility that simulator solution will be replaced into the bottles and reused in order to lower operating costs, which would of course degrade the accuracy of any calibration, or that less than the full volume of simulator solution would be used for each calibration if the bottles can be resealed.
Some agencies prepare simulator solution by diluting a precisely measured aliquot of a concentrated simulator solution with water or a suitable inert fluid. However, this process can introduce significant errors as the result of improper procedures used in measuring the fluid or mixing the concentrate with the fluid. Moreover, any degradation or corruption of the concentrate may be amplified when the concentrate is diluted